It is well recognized by the agricultural industry that it is advantageous to the end-users to be able to formulate dry agricultural chemicals such as fertilizers, pesticides, and/or adjuvants so that they can be easily mixed with water and applied by means of a spraying apparatus to a target area.
Mist, or the fine particles end of the droplet-size spectra in these agricultural sprays, i.e., those less than about 150 microns in diameter, often reduce the effectiveness of the chemical delivery process.
When the agricultural sprays are to be directed onto a specific target, the aerial spray or discharge delivery systems are typically mounted on airplanes, tractors, or ground rigs. However, as a result of spray drift, much of the active chemical ingredients in a spray can be rendered ineffective or lost because of the inability of the small diameter spray or mist particles to reach and impact upon the intended target, i.e., the crop or field locus. While small droplets provide better coverage of a target, they are more susceptible to drift than larger droplets. Spray drift represents a loss of agricultural chemical from intended targets and thus results in dangers inherent in air, ground, and water pollution. Since off-target agricultural chemicals are wasted product and can have a negative environmental and economic impact, especially if the agricultural spray medium contains fertilizer and most especially if the medium contains pesticide, it behooves sprayers to reduce this drift induced problem.
In many farming areas, soil is deficient in one or more of the natural nutrients required for satisfactory growth of certain crops. As a result, such crops do not give their optimum yield. When such conditions exist, it is a common procedure to apply a fertilizer rich in the required nutrients(s). The most common fertilizers in use today are the water-soluble, nitrogen-containing fertilizers. Solutions of the fertilizers are usually applied to the crop locus via aqueous spraying techniques; and, as described above, this spraying process usually results in the attendant production of fine mist and droplet drift.
One solution proposed in the art to reduce mist and chemical drift in aqueous agricultural sprays, such as those containing fertilizers, is to incorporate into the aqueous medium a viscosity-increasing amount of a guar gum or derivative of guar gum, specifically non-derivatized guar gum, non-cationic derivatized guar gum, cationic guar gum, or mixtures thereof
Although guar gum is often referred to as a cold water swelling polymer, guar gum hydrates in either cold or hot water give high viscosity solutions. The viscosity development depends, to a certain extent, on particle size, pH, and temperature. Guar gum solutions are stable over the pH range of 4.0-10.5. Aqueous solutions of non-derivatized guar gum are often somewhat cloudy because of the small amount of insoluble fiber and cellulosic material present.
All of the commercially important derivatives of guar gum are formed by etherification reactions. The hydroxy alkyl as well as carboxy methyl derivatives tend to be much clearer and more stable than the non-derivatized guar gum. Improved clarity results from the derivatizations and solubilizations of insoluble seed impurities.
However, the aqueous hydration of dry, water-soluble polymers such as guar gum and/or its derivatives in an aqueous agricultural spray medium in order to realize drift reduction properties can often be an arduous and frustrating task for the end-user.
Insufficient dispersion of powdered guar gum caused most often by the too rapid addition of the powder to the aqueous medium or insufficient agitation of the medium during the guar gum addition process of times results in agglomeration or lumps of guar gel. The lumps of guar gel, "fish-eyes", or other inhomogeneity of the mixture can result in difficulty in spraying and loss of drift control. These gel lumps not only cause a lowering of the overall concentrations of dissolved guar gum in the spray medium, and, thus, a reduced drift control of the medium, but also result in medium that will not flow or be readily pumpable and a plugging of the spray nozzle holes. The agglomeration or gellation can be reduced in many cases by adding the guar gum to the aqueous system very slowly with vigorous agitation. Slow addition, however, substantially reduces the efficiency and speed of the end-users processes. For the above reasons, agricultural end-users, such as farmers, continue to desire a fast, effective and simple way of incorporating guar gum and/or its derivatives into their aqueous systems.
By physically pre-blending water-soluble nitrogen-containing fertilizer such as diammonium sulfate with any of the above-described guar gum or guar gum derivatives such as hydroxy propyl guar, formulators can present to the agricultural end-user a dry system that can be easily handled in that, for example, bulky liquid containers do not have to be stored, recycled, etc. and the end-user need not be concerned about ensuring that the weight ratios of fertilizer to drift reduction agent are correct.
Applicants have discovered that, serendipitously, the pre-blended composition of water-soluble nitrogen-containing fertilizer and the guar gum drift reduction agent has the added advantages of enhancing the uniform dispersion and hydration of the guar agent by significantly reducing the agglomeration and gellation problems inherent in the aqueous hydration of powdered guar and its derivatives. Although not wishing to limit the scope of this discovery, the inventive scope to be set forth and determined solely by the claims, it is believed that the water-soluble, nitrogen-containing fertilizers, such as diammonium sulfate which tend to be crystalline, and, thus, are of a higher density than the drift reduction agents, at the outset, initially provide a solid barrier which physically separates the guar gum agent particles, i.e., provides a dilution effect. Secondly, by being of a relatively higher density, the fertilizer crystals tend to quickly pull the guar gum agent particles toward the bottom, i.e., down through the aqueous agricultural medium. The above two effects apparently ensure that a maximum surface area of the guar gum agents remains exposed to the aqueous medium and, thus, the overall hydration rate is enhanced.
Although the pre-blends of water-soluble, nitrogen-containing fertilizer and guar gum drift reduction agent are a decided improvement in the art and provide significant and unexpected advantages to the end-users as described above, problems still occur in actual field use of these blends when end-users, such as farmers, attempt to add the dry blend to a medium which may already contain an agricultural chemical or adjuvant formulation. This is because pesticides and/or adjuvants routinely contain surfactants which generate foam under agitation conditions prevalent in typical spray application equipment. With the presence of foam during the addition of the dry blends, the dispersion of the fertilizer blends is reduced and gelling and agglomeration problems often return.
Accordingly, users of water-soluble, nitrogen-containing fertilizers continue to desire a dry blend containing these fertilizers that can be incorporated into aqueous spray mixtures rapidly and completely to achieve drift reduced, sprayable agricultural media without the formation of agglomerates, gels, or clumps and which can be readily and safely handled in dry form.